Coatings, composition, and method related to non-spalling low density hardface coatings

Abstract

A composite body that is spall resistant and comprises a substantially discontinuous cermet phase in a substantially continuous metal rich matrix phase. The composite body is typically bonded to a substrate to form a hardfacing on the substrate. The composite body exhibits ductile phase toughening with a strain to failure of at least about 2 percent, a modulus of elasticity of less than about 46 million pounds per square inch, and a density of less than about 7 grams per cubic centimeter. The metal rich matrix phase between the ceramic rich regions in the composite body has an average minimum span of about 0.5 to 8 microns to allow ductility in the composite body. The composite body has a Vicker's hardness number of greater than approximately 650. The discontinuous cermet phase is in the form of ceramic rich regions embedded within the composite body, and it includes ceramic particles and a cermet binder. The ceramic particles having a Moh's hardness of at least approximately 7.5, a modulus of elasticity of less than approximately 46 million pounds per square inch, and an average particle size of from about 0.1 to 10 microns. The ceramic rich regions exhibit high hardness as compared with the matrix phase.

What is claimed is: 
     
       1. A composite body, said composite body being spall resistant and comprising a discontinuous cermet phase in a metal rich matrix phase, said discontinuous cermet phase including ceramic particles comprised of SiAlON and a cermet binder, said ceramic particles having a Moh's hardness of at least approximately 8, a modulus of less than approximately 46 million pounds per square inch, and an average particle size of from about 0.1 to 10 microns, said composite body having a Vicker's hardness number of greater than approximately 650, a strain to failure of at least 1 percent, and a modulus of less than approximately 46 million pounds per square inch. 
     
     
       2. A method of forming a composite body on a substrate comprising:
 selecting a cermet particle comprising a cermet core particle including SiAlON ceramic particles, a cermet binder, and a metal rich matrix phase precursor, said metal rich matrix phase precursor comprising from about 20 to 70 volume percent of said cermet particle, said ceramic particles having a Moh's hardness of at least approximately 8, a modulus of less than approximately 46,000,000 pounds per square inch, and an average particle size of from about 0.3 to 8 microns; 
 injecting said cermet particle into a thermal spray generating device; 
 allowing said thermal spray generating device to generate a thermal spray including said cermet particle; 
 directing said thermal spray onto a substrate; and 
 allowing said composite body to form a coating on said substrate that exhibits residual stresses of generally between approximately 5,000 pounds per square inch compressive and approximately 3,000 pounds per square inch tensile, and is adhered to said substrate with an adhesive strength of greater than about 10,000 pounds per square inch gauge.